The present invention generally relates to trunk line bandwidth reservation systems, and more particularly to a trunk line bandwidth reservation system for reserving in an asynchronous transfer mode (ATM) switching system a bandwidth which will be required by a user when the user makes a communication.
According to the ATM switching system which forms a basis for realizing a broadband integrated services digital network (B-ISDN), various media may use transmission lines in common. On the other hand, there are demands to guarantee the service quality by assigning a bandwidth with respect to the medium in which the transmission speed varies with time.
Bandwidth assigning techniques using the statistical multiplexing effect or the like have been proposed. However, there is a problem in that it is difficult to accept a call in the medium which requires a broadband. Because this problem must be eliminated in order to guarantee the communication service quality, it is necessary for the switching system to control the bandwidth assignment with respect to the users so that the required bandwidth is secured.
In a conventional bandwidth assigning technique in the ATM switching system, the user declares parameters related to the bandwidth which will be used for the communication. The declared parameters include a maximum speed, an average speed, service quality class identifier and the like. The ATM switching system fixedly assigns the bandwidths starting from the free bandwidth which can be used for the transmission or, assigns the bandwidths on a probability basis, based on the declared parameters. In this case, the bandwidths which are used differ depending on the kind of medium such as audio, data and image and depending on the different speeds of the media. When transmitting the image, the transmission rate is on the order of several tens of Mbps and a relatively large bandwidth is used. The image transmission can provide various kinds of services such as point-to-point image communication, video conference, and broadcasting from a transmitting station to a plurality of receiving stations.
According to the conventional bandwidth assigning technique described above, the bandwidth assignment is made by the switching system at the time when the user actually makes the communication by declaring the parameters. For this reason, even if a bandwidth assignment for a broadband is requested at a predetermined time in order to make the image broadcast communication described above, for example, the free bandwidth which can be used for this communication may be insufficient depending on the state of use of the transmission lines. In this case, the image broadcast communication cannot be accepted, and there is a problem in that the system cannot provide the service with respect to the user.
Accordingly, it is a general object of the present invention to provide a novel and useful trunk line bandwidth reservation system in which the problem described above is eliminated.
Another and more specific object of the present invention is to provide a trunk line bandwidth reservation system for an asynchronous transfer mode switching system which is coupled to a plurality of terminals, comprising data storage means for storing reservation data, bandwidth reservation means, coupled to the data storage means, for registering a reservation datum which includes at least a time zone and a reserved bandwidth to be used by a reserved communication into the data storage means in response to a reservation request which includes the reservation datum and is generated from a first terminal before the time zone, where the time zone starts from a reserved start time, and bandwidth assignment means, coupled to the bandwidth reservation means, for assigning the reserved bandwidth to the first terminal in response to a connect request which is generated from the first terminal at the reserved start time, and for assigning an available bandwidth to a second terminal in response to a connect request which is generated from the second terminal by judging the available bandwidth based on a bandwidth which is presently in use and the reserved bandwidth which is secured by the reservation datum, where the second terminal is other than the first terminal and generates the connect request which is no associated with a reservation request, and the data storage means, the bandwidth reservation means and the bandwidth assignment means are provided within the asynchronous transfer mode switching system. According to the trunk line bandwidth reservation system of the present invention, it is possible to positively assign the requested bandwidth to each user. As a result, it is possible to stably provide services of a high quality, including services related to image transmission. Therefore, it is possible to improve the reliability of the communication system which employs the present invention.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.